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Persistent decrease in synaptic efficacy induced by nicotine at Schaffer collateral–CA1 synapses in the immature rat hippocampus
Author(s) -
Maggi Laura,
Sola Elisabetta,
Minneci Federico,
Le Magueresse Corentin,
Changeux Jean Pierre,
Cherubini Enrico
Publication year - 2004
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2004.067041
Subject(s) - neuroscience , cholinergic , nicotine , postsynaptic potential , synaptic plasticity , hippocampus , nicotinic agonist , schaffer collateral , nmda receptor , neural facilitation , ampa receptor , glutamate receptor , neurotransmission , long term potentiation , excitatory postsynaptic potential , biology , chemistry , medicine , inhibitory postsynaptic potential , receptor
Neuronal nicotinic acetylcholine receptors (nAChRs) are widely distributed within the brain where they contribute to the regulation of higher cognitive functions. The loss of the cholinergic function in Alzheimer's disease patients, along with the well‐known memory enhancing effect of nicotine, emphasizes the role of cholinergic signalling in memory functions. The hippocampus, a key structure in learning and memory, is endowed with nAChRs localized at pre‐ and postsynaptic levels. In previous work on the immature hippocampus we have shown that, at low probability ( P ) synapses, activation of α7 nAChRs by nicotine or by endogenously released acetylcholine persistently enhanced glutamate release and converted ‘presynaptically silent’ synapses into functional ones. Here we show that in the same preparation, at high P synapses, nicotine induces long‐term depression of AMPA‐ and NMDA‐mediated synaptic currents. This effect was mediated by presynaptic α7‐ and β2‐containing receptors and was associated with an increase in the paired pulse ratio and in the coefficient of variation. High P synapses could be converted into low P and vice versa by changing the extracellular Ca 2+ /Mg 2+ ratio. In these conditions nicotine was able to persistently potentiate or depress synaptic responses depending on the initial P ‐values. A bi‐directional control of synaptic plasticity by nicotine would considerably enhance the computational properties of the network during a critical period of postnatal development thus contributing to sculpt the neuronal circuit.